The "legacy pack" screenshots show a T'Varo firing dual beams from its nacelles. This is ugly. Please don't do this, it frankly looks dumb. Maybe on Federation ships that have some beefy nacelles is this acceptable.
On the other hand, the animated banner-add for the legacy pack has a T'Varo firing dual beams from the hull. This looks excellent. Do this!
Dual Beams just fire out of whatever DHC mounting a ship has, which is generally on the wingtips of winged ships. It would be nice if they changed this to work with a ship's beam array mountings, but you're almost certainly going to be stuck with what it is.